The present invention relates to a plow blade lifted by a hydraulic cylinder and, more particularly, to an improved lift arm for securing a chain which raises and lowers the plow blade.
Particular applicability of the invention is derived from use in connection with a front mounted hydraulic lift assembly. Mounted on portions of a frame of a vehicle, the hydraulic lift assembly is controlled from within the operator cab. The plow blade is pivotably mounted at a front portion of the vehicle frame. Mounted above the vehicle frame is a hydraulic cylinder arrangement for controlling the raising and lowering of the plow blade. In order to effect movement of the plow blade, one end of the lift arm is pivotably connected to a frame member of the vehicle. Connected between the ends of the lift arm is a piston rod of the hydraulic cylinder. Generally, a link chain connects the plow blade to the outer free end of the lift arm.
In the past, many arrangements have been used to connect the chain to the pivoted lift arm. One of these arrangements involves a lift arm having a narrow, perpendicular open slot at its outermost end for receiving one link of the chain. This slot provides the sole connection between the chain and the lift arm. If rough surfaces were encountered by the plow blade, the rapid and abrupt upward movement of the blade could result in the chain becoming free from the open slot. With the chain disconnected, reassembly of the chain to the lift arm is required. Prior art attempts at restraining the chain from being released from the slot frequently result in complication of the assembly procedures of the chain to the lift arm.
Presently, the chain is connected to the lift arm by a chain link restrained within the narrow slot such that the connecting link is constantly perpendicular to the face of the lift arm. When the blade is raised or lowered, the angle of the chain relative to the lift arm is continuously changing. Raising and lowering the blade therefore causes movement between interconnected links of the chain and, more particularly, movement between the link which is secured in the slot of the lift arm and the next lower link.
Constant movement between the interconnected links of the chain results in wear of the link material. Excessive wear can eventually lead to weakening of a particular link in the chain. Replacement of the chain within the plow assembly presents an extensive problem. The link chain is generally connected to plow blades by welding the chain directly to a portion of the blade. If the chain is required to be replaced, as a result of weakening of a link, the old chain must be cut loose and a new chain welded to the blade.